Our work on heritable forms of cancer in man suggests that "non-tumor" cutaneous cells can be utilized for diagnosis of clinically latent manifestations of neoplasia. Abnormal phenotypic expressions have been identified in cultured skin fibroblasts (SF) derived from normal appearing skin biopsies of tumor-prone and tumor-bearing individuals with hereditary adenomatosis of the colon and rectum (ACR). These consisted of growth disorders, increased proteolytic activity, cytoskeletal alterations, and increased susceptibility to transformation by the Kirsten murine sarcoma virus. Apparently, systemic disorders occurring within stromal cells of individuals at high risk of cancer are intrinsically linked to cancer and will be used in studies concerning cancer causation and cancer progression. The present report concerns (1) expression of neoantigens by skin fibroblasts derived from normal and ACR phenotypes prior to and following infection by DNA and RNA oncogenic viruses and (2) the ability of SF derived from normal and ACR phenotypes to repair irradiation-induced defective SV40 virus functions in the infected cells.